CN112152048A - A system for generating coherent THz radiation sources with few periods and high field strengths - Google Patents

Abstract

The invention discloses a system for generating a coherent THz radiation source with few cycles and high field strength, comprising an ultra-short pulse laser (100) and a vacuum target chamber system (101), wherein a supersonic nozzle system is arranged in the vacuum target chamber system (101). (102), a short focal distance axis parabolic mirror (103), an off-axis parabolic mirror (104) and an optical path system, the ultra-short pulse laser (100) is connected to the short focal distance axis paraboloid mirror (103), the short focal distance axis paraboloid The mirror (103) is connected to the supersonic nozzle system (102), the supersonic nozzle system (102) is connected to the off-axis parabolic mirror (104), and the off-axis parabolic mirror (104) is connected to the optical path system; based on the femtosecond laser pulse and the supersonic jet target or air chamber The way of interaction produces a high-power THz radiation source.

Description

A system for generating coherent THz radiation sources with few periods and high field strengths

technical field

The invention relates to the technical field of terahertz light sources, in particular to a system for generating coherent THz radiation sources with few periods and high field strength.

Background technique

Terahertz (T-ray) light sources are considered the next generation of light sources, with applications ranging from cancer diagnosis to materials science. Due to its non-ionizing nature, good spatial resolution and ability to penetrate several millimeters of biological tissue. When it comes to cancer detection, T-rays are a suitable alternative to X-rays. In addition to biological imaging, powerful T-rays have many applications in materials science as a diagnostic tool, such as ultrafast spectroscopy. By focusing high-power T-rays to a millimeter spot size, electric fields on the order of GV/m can be generated. This electric field can be used to study the structural transition of polar molecules. Correlated Tesla-scale transient magnetic fields can be used to generate magnetic or spin excitations and track their dynamics on picosecond timescales. High-power T-ray sources are currently available from large facilities such as linear accelerators to compact light sources based on electro-optic crystals. In a linear accelerator, relativistic electrons are bunched by a curved magnet to produce a terahertz beam with a peak power of MW. Electro-optic crystal-based light sources use high repetition rate laser systems to generate T-rays through optical rectification in nonlinear crystals. Both sources have pros and cons. Accelerator-based T-ray sources, for example, are high peak power MW, high repetition rate sources, however, they are bulky and expensive, and thus offer rather limited availability. Based on optical rectification or more economical compact light sources, T-ray pulses comparable to accelerator light sources can be achieved, however, the damage threshold of nonlinear crystals limits the field strength of T-rays. Plasma does not have this limitation. Therefore, laser plasma THz light source has always been a hot research topic. In fact, there are various mechanisms by which T-rays are produced. For two-color laser-generated plasma filaments, the T-ray energy is as high as 5 µJ, and the conversion efficiency is 10 ^-4 . However, at higher laser intensities, terahertz radiation tends to saturate due to intensity clamping, low electron density, and reabsorption of radiation. The plasma generated during the interaction of high-power lasers with solids has no such limitation, and is also a known source of high-field T-rays, but less researched.

Prior art [1]: The proof-of-principle experiment by Yugami et al. of Utsunomiya University in Japan proved that in a perpendicularly magnetized plasma, ultra-short, ultra-high-power pulsed laser excited the Cherenkov wake to generate radiation (see the article https: https://doi.org/10.1103/PhysRevLett.89.065003). Radiated frequencies in the millimeter range (up to 200 GHz). The radiation intensity is proportional to the theoretically expected magnetic field strength. The polarization of the emitted radiation is also detected.

Prior art [2]: Yi et al. from Chalmers University of Technology, Switzerland, proposed a method to generate high-intensity terahertz (THz) pulses by irradiating plasmonic waveguides with high-power lasers. When the laser pulse enters the plasmonic waveguide, a highly charged electron beam is generated and accelerated to 100 MeV by the transverse electromagnetic mode. When the electron beam leaves the plasmonic waveguide, a significant portion of the electron energy is transferred to THz radiation by coherent diffracted radiation. The results show that 100 mJ-level relativistic strong terahertz pulses with tunable frequency can be generated on existing laser devices.

Prior art [3]: D'Amico of the Ecole Nationale Polytechnique discovered a THz radiation generated in the air (see article https://doi.org/10.1103/PhysRevLett.98.235002), this emission is based on strong Collimated terahertz beams are emitted forward, which they attribute to the transition in the wakefield of space charges traveling at the speed of light created after the ionization front—Cherenkov radiation. It uses normal air as the production medium and requires only a femtosecond laser beam without precise alignment. What's more, the terahertz radiation source can be easily positioned very close to the target, possibly several kilometers away, thus solving the problem of the transmission of terahertz radiation in the air. In terms of effective radiation from distant targets, this new terahertz radiation amplitude exceeds that of other radiation sources by orders of magnitude.

Prior art [4]: The research team of Sheng Zhengming from Shanghai Jiaotong University found that strong low-frequency radiation with a center frequency near the reciprocal of the driving pulse duration was observed at the vacuum-plasma interface (https://doi.org/10.1103/ PhysRevE.69.025401). The radiation originates from large-amplitude plasma waves excited at the plasma boundaries. For an incident pulse of 3×10 ¹⁷ W/cm ² , the induced radiation power can reach the order of megawatts, and the energy is only in the order of millijoules. It is found that the appropriate density scale length near the plasma boundary is beneficial to the generation of induced emission. This density distribution can be achieved by firing laser pulses laterally into the gas jet, or by adjusting the delay between the pre-pulse and the main pulse when a solid target is used.

In order to generate THz with high field strength more efficiently and realize the practical application of light source in related scientific fields, researchers have proposed various methods to improve the field strength and energy conversion efficiency of THz source. However, from the perspective of the prior art, in addition to the low conversion efficiency, there is also a problem that the laser is difficult to align, and a new technical solution needs to be found to solve it.

SUMMARY OF THE INVENTION

The purpose of the present invention is to design a coherent THz radiation source generating system with few periods and high field strength to generate high-power THz radiation source based on the interaction of femtosecond laser pulses and supersonic jet targets or gas chambers.

The present invention is realized by the following technical solutions: a low-period high-field-strength coherent THz radiation source generation system, including an ultra-short pulse laser and a vacuum target chamber system, wherein the vacuum target chamber system is provided with a supersonic nozzle system, a short focal distance On-axis parabolic mirror, off-axis parabolic mirror and optical path system, the ultra-short pulse laser is connected to the short focal distance axis parabolic mirror, the short focal distance axis parabolic mirror is connected to the supersonic nozzle system, the supersonic nozzle system is connected to the off-axis parabolic mirror, and the off-axis parabolic mirror Connect the optical system.

Further, in order to better realize the present invention, the following setting method is specially adopted: the optical path system includes a spectral beam splitter, a bandpass filter, a polarizer and a pyroelectric THz detector, and the off-axis parabolic mirror is sequentially connected to the spectrum. Beamsplitters, bandpass filters, polarizers and pyroelectric THz detectors.

Further, in order to better realize the present invention, the following setting method is particularly adopted: in the vacuum target chamber system, the spectral beam splitter, the bandpass filter, the polarizer and the pyroelectric THz detector are arranged on the same optical axis.

A short focal distance axis parabolic mirror, an off-axis parabolic mirror with a through hole, a spectral beam splitter, a bandpass filter, a polarizer and a pyroelectric THz detector are placed in the vacuum target chamber in order, coaxial and of equal height.

Further, in order to better realize the present invention, the following setting mode is particularly adopted: the ultrashort pulse laser adopts a mesa-type ultrashort pulse laser with a pulse width of less than 30 femtoseconds and a single-shot energy of less than 1 joule.

Further, in order to better realize the present invention, the following setting method is specially adopted: the supersonic nozzle system is placed in the center of the target chamber of the vacuum target chamber system, and the height of the center of the air column ejected by the supersonic nozzle system and the short focal distance axis paraboloid. The center of the mirror is the same height.

Further, in order to better realize the present invention, the following setting mode is particularly adopted: the supersonic nozzle system adopts Japan SMARTSHELL supersonic gas nozzle system, and its main structure is a controller, a solenoid valve and a supersonic nozzle.

Further, in order to better realize the present invention, the following setting method is particularly adopted: the short focal distance axis parabolic mirror with a relative aperture of F/3 is adopted as the short focal distance axis parabolic mirror.

Further, in order to better realize the present invention, the following setting method is specially adopted: the off-axis parabolic mirror is an off-axis parabolic mirror with a through hole, and the diameter of the through hole is 3 mm, the off-axis angle is 50.8 mm, and the reflection focal length is 101.6 mm. , the busbar focal length is 50.8 mm.

Further, in order to better realize the present invention, the following setting method is particularly adopted: the length of the laser pulse generated by the ultra-short pulse laser is much smaller than the wavelength of the plasma formed by the gas ionization of the supersonic nozzle of the supersonic nozzle system.

Compared with the prior art, the present invention has the following advantages and beneficial effects:

The present invention overcomes the limitation of the previous scheme of generating a high field strength THz source, and adopts a tightly focused femtosecond laser to interact with dilute helium gas. When the laser is transmitted in the dilute plasma, the time-varying displacement current is formed by the cavitation wake field generated by the laser, and then the spontaneous angular magnetic field is generated. Under the action of the self-generated angular magnetic field, electromagnetic waves are radiated through the Cherenkov radiation mechanism, and its frequency is slightly higher than the plasma frequency. When the gas density is constant, the radiated electromagnetic waves are THz waves.

The invention can obtain a THz ray source with extremely high field strength by the interaction of femtosecond laser with extremely short pulse width and supersonic jet, and can be used as a high-performance THz ray source for detection and diagnosis in the fields of security, biomedicine and the like .

The invention has the characteristics of high field strength (KV/meter), short time scale (sub-picosecond), high conversion rate (0.1%), small spatial divergence angle (100 milliradians level), and is suitable for high space-time resolution THz The ray detection neighborhood is also applicable to the field of biomedical imaging, and possibly to the field of matter manipulation.

The invention has the characteristics of high field strength. By using the magnetized Cherenkov wake field, the electric field strength of the radiated THz wave is tens of GV/m, which is much higher than the current mainstream THz source. Compared with the prior art [2], the field strength is comparable. According to literature research, it is the strongest THz electric field known so far.

The present invention has the characteristics of broad spectrum, and the generation medium of the THz wave of the present invention is plasma. Therefore, in essence, the THz wave must be broad-spectrum, the frequency spread can reach 100%, and the center frequency is located near the plasma wavelength, which is slightly higher than the plasma eigenfrequency.

The present invention has the characteristics of high time resolution. Since the working medium of the present invention is a nonlinear plasma wave, which has only 1-2 oscillation cycles, the THz radiation has only 1-2 plasma cycles, and the final total pulse width will be Less than 1 picosecond, with high time resolution.

The cost of the invention is controllable, and the technology involved in the invention is completely feasible after being verified by a high-power laser device. At present, the mature commercial repeated frequency terawatt lasers can fully meet the needs and do not require expensive external equipment, such as super-strong external magnetic field generators, which will greatly improve the THz radiation field strength, and will also minimize equipment procurement and cost. maintenance costs.

The present invention is simple and easy to implement. Compared with the prior art [2], the present invention can generate THz pulses with only one laser beam, and does not require complicated and precise alignment techniques, thus greatly reducing the difficulty of experiments. At the same time, compared with the prior art [3], expensive and inefficient measures to suppress the pre-pulse are not required.

Description of drawings

Figure 1 is a schematic structural diagram of the present invention.

Among them, 100-ultrashort pulse laser, 101-vacuum target chamber system, 102-supersonic nozzle system, 103-short focal distance axis parabolic mirror, 104-off-axis parabolic mirror, 105-spectral beam splitter, 106-bandpass filter, 107-polarizer, 108-pyroelectric THz detector.

Detailed ways

The present invention will be further described in detail below with reference to the examples, but the embodiments of the present invention are not limited thereto.

In order to make the purposes, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments These are some embodiments of the present invention, but not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but is merely representative of selected embodiments of the invention.

In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms and the like is based on the orientation or positional relationship shown in the accompanying drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying the indicated The device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

In addition, the terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

In the present invention, unless otherwise expressly specified and limited, the terms "installed", "connected", "connected", "fixed" and other terms should be understood in a broad sense, for example, it may be a fixed connection or a detachable connection , or as one. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

In the present invention, unless otherwise expressly specified and limited, a first feature "on" or "under" a second feature may include the first and second features in direct contact, or may include the first and second features Not directly but through additional features between them. Also, the first feature being "above", "over" and "above" the second feature includes the first feature being directly above and obliquely above the second feature, or simply means that the first feature is level higher than the second feature. The first feature is "below", "below" and "below" the second feature includes the first feature being directly below and diagonally below the second feature, or simply means that the first feature has a lower level than the second feature.

It is worth noting that: in this application, when certain known technologies or conventional technical means need to be applied in the field, the applicant may have no specific description in the text of what the known technology or/and conventional technical means are. However, it cannot be considered that the present application does not comply with the third paragraph of Article 26 of the Patent Law because the technical means is not specifically disclosed in the text.

Example 1:

As shown in FIG. 1 , a system for generating a coherent THz radiation source with few periods and high field strength includes an ultra-short pulse laser 100 and a vacuum target chamber system 101. It is characterized in that: the vacuum target chamber system 101 is provided with a supersonic nozzle system. 102. A short focal distance axis parabolic mirror 103, an off-axis parabolic mirror 104 and an optical path system, the ultra-short pulse laser 100 is connected to the short focal distance axis parabolic mirror 103, and the short focal distance axis parabolic mirror 103 is connected to the supersonic nozzle system 102, and the supersonic nozzle The system 102 is connected to the off-axis parabolic mirror 104, and the off-axis parabolic mirror 104 is connected to the optical path system.

As a preferred setting scheme, the low-period high-field-strength coherent THz radiation source generation system is provided with an ultra-short pulse laser 100 for generating laser light and a vacuum target chamber system 101 for converting laser waves into a THz radiation source. The vacuum target chamber system 101 It includes a supersonic nozzle system 102, a short focal distance axis parabolic mirror 103, an off-axis parabolic mirror 104 and an optical path system; the optical path of the ultra-short pulse laser 100 is connected to the short focal distance axis parabolic mirror 103, and the short focal distance axis parabolic mirror 103 focuses the laser and projects it onto the edge of the plasma formed by the supersonic nozzles of the supersonic nozzle system 102 .

In specific use, a commercial laser device (ultrashort pulse laser 100 ) generates an ultrashort laser pulse with a pulse width of only a few laser cycles, which is focused to the supersonic nozzle system through a short focal distance axis parabolic mirror 103 with a relative aperture of F/3 On the edge of the plasma formed by the supersonic nozzle of 102, the laser pulse pushes the electrons away from both the lateral and radial directions, forming a nonlinear plasma wave. Since the ion background remains stationary, under certain density conditions, a vacuolar structure is formed inside the plasma, and there is no electron beam loaded in the vacuoles. The pushed electrons flow back, creating a large-scale angular magnetic field with a strength of tens of tesla. Under the action of this angular magnetic field, the plasma oscillation is transformed from a purely electrostatic type to a partial electromagnetic type. Finally, the electromagnetic radiation is released at a frequency close to the oscillation of the plasma, forming a THz radiation wave of extremely high field strength. In order to separate the laser light passing through the supersonic nozzle system 102, an off-axis parabolic mirror (preferably an off-axis parabolic mirror with a through hole) 104 is arranged on the optical path. Large THz radiation waves are collected by off-axis parabolic mirrors 104 with through holes. In addition, an optical path system is provided on the optical path for further separation and detection.

Example 2:

This embodiment is further optimized on the basis of the above-mentioned embodiment, and the above-mentioned technical solutions and the above-mentioned technical solutions will not be repeated here, as shown in FIG. The following setting method: the supersonic nozzle system 102 is placed in the center of the target chamber of the vacuum target chamber system 101 , and the center height of the air column ejected by the supersonic nozzle system 102 is the same height as the center of the short focal distance axis parabolic mirror 103 . The ultra-short pulse laser 100 adopts a mesa-type ultra-short pulse laser with a pulse width of less than 30 femtoseconds and a single-shot energy of less than 1 joule.

As a preferred setting scheme, the ultrashort pulse laser 100 adopts a mesa-type ultrashort pulse laser with a center wavelength of 0.8 microns, a peak power of several terawatts, a repetition rate of 10 Hz, a pulse width of less than 30 femtoseconds, and a single-shot energy of less than 1 joule.

Example 3:

This embodiment is further optimized on the basis of any of the above-mentioned embodiments, and the above-mentioned technical solutions and the above-mentioned technical solutions will not be repeated here. As shown in FIG. 1, in order to better realize the present invention, In particular, the following setting method is adopted: the optical path system includes a spectral beam splitter 105, a bandpass filter 106, a polarizer 107 and a pyroelectric THz detector 108, and the off-axis parabolic mirror 104 is sequentially connected to the spectral beam splitter 105, the bandpass Pass filter 106 , polarizer 107 and pyroelectric THz detector 108 .

In order to control the output spectral bandwidth, a band-pass filter 106 is placed after the spectral splitter 105. The preferred band-pass filter can be configured with different bandwidths as required, and different band-pass filters can be used to select different bandwidths. After the bandpass filter 106, a polarizer 107 is placed. With the polarizer 107, the polarization direction of the THz wave can be selected. Finally, the filtered and polarization-selected THz waves are detected by the pyroelectric THz detector 108 .

Example 4:

This embodiment is further optimized on the basis of any of the above-mentioned embodiments, and the above-mentioned technical solutions and the above-mentioned technical solutions will not be repeated here. As shown in FIG. 1, in order to better realize the present invention, In particular, the following setting method is adopted: the supersonic nozzle system adopts the Japanese SMARTSHELL supersonic gas nozzle system, and its main structure is a controller, a solenoid valve and a supersonic nozzle.

Example 5:

This embodiment is further optimized on the basis of any of the above-mentioned embodiments, and the above-mentioned technical solutions and the above-mentioned technical solutions will not be repeated here. As shown in FIG. 1, in order to better realize the present invention, In particular, the following setting method is adopted: the short focal distance axis parabolic mirror 103 adopts a short focal distance axis parabolic mirror with a relative aperture of F/3.

Example 6:

This embodiment is further optimized on the basis of any of the above-mentioned embodiments, and the above-mentioned technical solutions and the above-mentioned technical solutions will not be repeated here. As shown in FIG. 1, in order to better realize the present invention, In particular, the following setting method is adopted: the length of the laser pulse generated by the ultra-short pulse laser 100 is much smaller than the wavelength of the plasma formed by the ionization of the gas in the supersonic nozzle of the supersonic nozzle system 102 .

Example 7:

This embodiment is further optimized on the basis of any of the above-mentioned embodiments, and the above-mentioned technical solutions and the above-mentioned technical solutions will not be repeated here. As shown in FIG. 1, in order to better realize the present invention, In particular, the following setting method is adopted: the off-axis parabolic mirror 104 is an off-axis parabolic mirror with a through hole, and the diameter of the through hole is 3 mm, the off-axis angle is 50.8 mm, the reflection focal length is 101.6 mm, and the busbar focal length is 50.8 mm.

Example 8:

As shown in Figure 1, a low-period high-field-strength coherent THz radiation source generation system includes

Designed with optical parametric chirped pulse amplification technology, the center wavelength is 0.8 microns, the peak power is several terawatts, the repetition frequency is 10 Hz, the pulse width is less than 30 femtoseconds, and the single-shot energy is less than 1 Joule. short pulse laser 100);

Vacuum target chamber system 101 for carrying out supersonic nozzle system 102, short focal distance axis parabolic mirror 103, off-axis parabolic mirror 104, spectral beam splitter 105, bandpass filter 106, polarizer 107 and pyroelectric THz detector 108 package.

Among them, the supersonic nozzle system 102 is placed behind the short focal distance axis parabolic mirror 103, and adopts the supersonic nozzle system of Japan's SMARTSHELL supersonic gas nozzle system (its main structure is a controller, a solenoid valve and a supersonic nozzle);

The short focal distance axis parabolic mirror 103 is placed behind the ultra-short pulse laser 100, and adopts a short focal distance axis parabolic mirror with a relative aperture of F/3;

The off-axis parabolic mirror 104 is an off-axis parabolic mirror with a through hole, and is placed behind the supersonic nozzle of the supersonic nozzle system 102 to realize laser separation;

Spectral beam splitter 105, placed after the off-axis parabolic mirror 104, is used to separate the THz radiation;

A bandpass filter 106, placed after the spectral splitter 105, is used to control the output spectral bandwidth;

The polarizer 107 is placed after the bandpass filter 106, and is used to select the polarization direction;

The pyroelectric THz detector 108, placed behind the polarizer 107, uses the pyroelectric effect of electromagnetic waves to detect the THz radiation wave, which is detachable and can be assembled or removed as required.

In application, the ultrashort pulse laser 100 emits a space-time double Gaussian ultrashort intense laser pulse. The space-time double Gaussian ultra-short intense laser pulse has a length of less than 30 femtoseconds and an energy of 0.1 joules. The short focal distance axis parabolic mirror 103 is focused to the supersonic nozzle edge of the supersonic nozzle system 103 , so that the laser beam waist size is 13 μm, and the corresponding peak laser power density is 1.37×10 ¹⁸ W/cm ² . The polarization direction of the laser light is S polarization. The back pressure of the supersonic nozzle was adjusted so that the plasma density after laser pre-pulse ionization was 1×10 ¹⁸ /cm ³ , and the corresponding plasma wavelength was 33 μm. From a large number of numerical calculations, it is found that a double vacuole structure is generated inside the plasma. The vacuole can be approximately regarded as a sphere, and the radius of the sphere is slightly larger than the beam waist of the driving laser. At the same time, the electrons displaced by the laser flow back under the action of electrostatic force and form an angular magnetic field. The magnitude of the magnetic field is 30 T. At this time, the non-magnetized plasma becomes a partially magnetized plasma. However, since the magnetic field is not too strong, the plasma is in a weakly magnetized plasma state at this time. Under the action of the angular magnetic field, the plasma wave changes from a purely electrostatic mode to a partial electromagnetic mode. Therefore, THz radiation with field strength greater than 20 GV/m can be generated, and the radiation frequency is characterized by a broad spectrum with a center frequency of 15 THz. Such a strong THz wave is very suitable for excitation and manipulation of polarized material molecules.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Any simple modifications and equivalent changes made to the above embodiments according to the technical essence of the present invention are all within the protection of the present invention. within the range.

Claims (9)

1. A system for generating a coherent THz radiation source with few periods of high field strength, comprising an ultra-short pulse laser (100) and a vacuum target chamber system (101), characterized in that: the vacuum target chamber system (101) is provided with a supersonic speed A nozzle system (102), a short focal distance axis parabolic mirror (103), an off-axis parabolic mirror (104) and an optical path system, the ultra-short pulse laser (100) is connected to the short focal distance axis parabolic mirror (103), the short focal distance The axial parabolic mirror (103) is connected to the supersonic nozzle system (102), the supersonic nozzle system (102) is connected to the off-axis parabolic mirror (104), and the off-axis parabolic mirror (104) is connected to the optical path system. 2. A system for generating coherent THz radiation sources with few periods and high field strength according to claim 1, characterized in that: the supersonic nozzle system (102) is placed in the center of the target chamber of the vacuum target chamber system (101), and The height of the center of the air column ejected by the supersonic nozzle system (102) is the same height as the center of the short focal distance axis parabolic mirror (103). 3. The system for generating a coherent THz radiation source with few periods and high field strength according to claim 1, wherein the ultrashort pulse laser (100) adopts a pulse width of less than 30 femtoseconds and a single-shot energy of less than 1 joule mesa-type ultrashort pulse laser. 4 . The system for generating coherent THz radiation sources with few periods and high field strength according to claim 1 , wherein the supersonic nozzle system ( 102 ) adopts a SMARTSHELL supersonic gas nozzle system. 5 . 5 . The system for generating coherent THz radiation sources with few periods and high field strength according to claim 1 , wherein the short focal distance axis parabolic mirror ( 103 ) adopts a short focal distance axis paraboloid with a relative aperture of F/3. 6 . mirror. 6. A low-period high-field-strength coherent THz radiation source generating system according to claim 1, characterized in that: the length of the laser pulse generated by the ultra-short pulse laser (100) is much smaller than that of the supersonic nozzle system (102 ) of the plasma wavelength formed by the ionization of the gas charged by the supersonic nozzle. 7. The system for generating coherent THz radiation sources with few periods and high field strengths according to any one of claims 1 to 6, wherein the optical path system comprises a spectral beam splitter (105), a bandpass filter (106 ), a polarizer (107) and a pyroelectric THz detector (108), the off-axis parabolic mirror (104) is sequentially connected to a spectral beam splitter (105), a bandpass filter (106), a polarizer (107) and Pyroelectric THz detector (108). 8 . The system for generating coherent THz radiation sources with few periods and high field strength according to claim 7 , wherein: in the vacuum target chamber system ( 101 ), a spectral beam splitter ( 105 ), a bandpass filter (106), polarizer (107) and pyroelectric THz detector (108) are arranged on the same optical axis. 9. The system for generating coherent THz radiation sources with few periods and high field strength according to claim 7, wherein the off-axis parabolic mirror (104) is an off-axis parabolic mirror with a through hole, and the diameter of the through hole is It is 3 mm, the off-axis angle is 50.8 mm, the reflection focal length is 101.6 mm, and the busbar focal length is 50.8 mm.

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